Add new `RSpec/NegatedExpectation` cop #1976

Job	Run time
Test coverage	20s
Confirm config and documentation	14s
Edge RuboCop: internal_investigation	17s
Ruby 2.7: internal_investigation	27s
Edge RuboCop: spec	21s
RSpec 4	25s
Ruby 2.7: spec	33s
Ruby 3.0: internal_investigation	13s
Ruby 3.0: spec	22s
Ruby 3.1: internal_investigation	16s
Ruby 3.1: spec	22s
Ruby 3.2: internal_investigation	12s
Ruby 3.2: spec	20s
Ruby 3.3: internal_investigation	14s
Ruby 3.3: spec	26s
Ruby ruby-head: internal_investigation	16s
Ruby ruby-head: spec	22s
Ruby jruby-9.4: internal_investigation	1m 18s
Ruby jruby-9.4: spec	1m 24s
	8m 22s

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